G15 Clutch slip-got a cure?

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
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G15 Clutch slip-got a cure?

Postby bjork » Tue Jun 19, 2007 10:34 pm

Hi all, my G15 is going nicely now, having been fully run-in on the trip to the international and back. Trouble is, I can't stop the clutch slipping. Have tried all the usual fixes (that I can think of) so does anyone know of a way of getting this marginal clutch working/replaced? Any one fitted a Japanese one Anyone got a supply of super duper grippy plates?
I hear that Norvil now do a belt drive kit for these bikes, but don't want to spend that much if I can help it. Plus it I imagine it has a Commando clutch and I don't think they are THAT great an improvement.
It does go nicely though I can't help myself-I have to keep winding it up to hear that lovely noise. What vibration
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G15 Clutch slip-got a cure?

Postby StuartN » Wed Jun 20, 2007 6:07 pm

I fitted a Norvil belt drive to my G15. On the positive side it runs dry so there is no problem with slip and take up is progressive. Installation was a pig, however. There is not enough room inside the primary cases. I had to grind ribs off the inner case and remove material around inspection hole on the front case to avoid it fouling on the belt. Even with these mods I can only run a 20mm belt which seems a bit marginal. I am in the process of making a 3/8" spacer between the inner and outer case so I can run a 30mm belt. Only other alternative might be stronger springs and go for a hydraulic clutch conversion.

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G15 Clutch slip-got a cure?

Postby bjork » Wed Jun 20, 2007 11:37 pm

Hi Stuart, and thanks for the info on the Norvil kit. I spoke to a G15 owner in Germany last month (Dirk from Cuxhaven) who had fitted a belt drive to his. He mentioned the 20mm belt in the Norvil kit but had made his own set up using a wider belt and a spacer between the cases as you describe.
I have tried winding the springs down as far as possible, even till it was impossible to get the clutch to disengage properly-still slips! It has all new plates and springs etc and an oil seal on the pushrod too. Have left plenty of clearance on the pushrod adjustment etc. Strange thing is, it slips from cold then as the transmission warms up seems to find more grip!
I just read your earlier post about oiling-wasn't just wet sumping was it? I didn't even try to remove or fit the head in situ! I removed the engine and then take the head off with the barrel-much easier.
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G15 Clutch slip-got a cure?

Postby Don Madden » Thu Jun 21, 2007 12:00 am

What oil are you using? Forget the original maker's recommendations. Modern engine oils are very slippery. I use ATF in all primaries that don't share oil with other parts of the bike.

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G15 Clutch slip-got a cure?

Postby G15 Roy » Thu Jun 21, 2007 7:40 am

Steve I fitted a belt driven clutch in a G15 and had four-alloy spacer made. I still have three left. If you go down the route give me a ring.
Roy

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G15 Clutch slip-got a cure?

Postby bjork » Thu Jun 21, 2007 9:05 pm

Hi Don, yes I am using ATF too and have done since it was built. I was concerned about oil from the gearbox getting in via the pushrod, so have sealed that too. Each time I strip the clutch the plates seem greasy but no worse than the other twins I've worked on. That's why I described it as a marginal clutch-it's just about coping with a 650 and needs careful set up even there-I just don't think it's up to the Atlas engines torque. If it had more plates/surface area I think it would cope, that's why I asked about Japanese clutches-I would be tempted to try and fit one!

Hi again Roy, thanks for the offer of the spacer I will keep it in mind. I'm still hoping to avoid that route for now, but the wind will no doubt change tomorrow!

There must be a special friction material that will cope here? I had a set of plates for my G80 from JSL a few years ago, they had a co-efficient of friction that must have been off all known scales! as soon as the clutch was engaged the plates stuck together and would not slip-you could pull the clutch lever in and the thing would still drive! Yoy needed to blip the throttle to jerk them free so gearchanges were accompanied by a blip both up and down. You didn't need to tension the pressure plate springs, they were now only there to hold the pressure plate on and return the release mechanism. I still have those plates in the garage shame they won't fit the AMC clutch. Just one of those added would probably fix the problem.
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G15 Clutch slip-got a cure?

Postby Don Madden » Thu Jun 21, 2007 10:24 pm

On my G12CSR with 5 plate Barnett clutch it would alsto slip a little when cold but would hold after the oil got warm. Of course the G15 has much more oomph than any G12.

Do you have stock gearing? The taller the gearing, the more load on the clutch.

Cheers, Don.

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G15 Clutch slip-got a cure?

Postby bjork » Thu Jun 21, 2007 11:40 pm

You're right Don, I have raised the gearing to almost CSR levels. 21 tooth crank sprocket and 19 tooth gearbox. I have fitted wide high bars so am up there in the breeze adding to the problem.
Ref your mention of warming the oil, I have wondered whether I need to soak friction plates in oil? as is the norm with japanese wet clutches. Apparantly that is what Surflex plates need?
Think I'll look on the NOC site as I haven't been there for a while!
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G15 Clutch slip-got a cure?

Postby Don Madden » Fri Jun 22, 2007 2:45 am

I do dip my lined plates in the ATF before I put them in.

Also use the dimpled plates as later type.

Cheers, Don.

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